In a wireless charging system, a wireless charging mat may wirelessly transmit power to a portable electronic device that is placed on the mat. A portable device may have a receiving coil and rectifier circuitry for receiving wireless alternating-current (AC) power from a coil in the wireless charging mat that is overlapped by the receiving coil. The rectifier converts the received AC power into direct-current (DC) power.
Charging efficiency may not be as high as desired with this type of wireless charging arrangement. There may also be a relatively large amount of cost and complexity associated with forming coils in a wireless charging mat.